Error code 146, when you turn on the computer it keeps on spinning

A DST Error code (such as your 0146) means that your hard disk drive has failed. You will need to purchase a replacement hard drive for your system.
If you turn the laptop over there will be an icon that looks like 3 discs stacked or it will say HD for the screws needed to remove the panel. Once you have access to the hard drive check for screws (typically one or two) and then gently remove the drive and unplug it from the system (typically it slides out of the plug and then lifts from the case).
You will install the new hard drive by placing it in and sliding it into place. Replace the screws and then the panel. Screw in the panel. If you were provided with Restore Discs you will need them to get your system running again.
If no discs were provided then you had a partition on the failed drive and you will need to purchase a copy of Microsoft Windows 7 Home Premium Full Retail to get it back up and running again.
You will also want to visit the dell site and download the latest drivers for your system and Windows 7.
While you are buying a new hard drive I would recommend purchasing enough memory to max out your system at 2GB. The memory chips will be under a panel with an Icon that looks like a computer chip or marked M. Some Models will have all slots under this panel and others will have one here and one that requires you to remove the keyboard (screws marked with a keyboard Icon or K).
Unfortunately your data is most likely inaccessible from your old hard drive.